An object-based storage system combines advantages of a network-attached storage (NAS) and a storage area network (SAN); therefore, the object-based storage system begins to serve as a main storage structure in a data storage system currently. An object is a basic unit in the object-based storage system, includes file data and relevant attribute information, and is easy to manage. An object-based storage device (OSD) is a basic constituent unit of a distributed object-based storage system, and is responsible for storage of an object. In order to ensure reliability of a stored object, for a same object, methods of multiple duplicates and an erasure code are used for protection. That is, as shown in FIG. 1, one object is stored in different OSDs, each OSD stores a part of data of the object, and parity data obtained according to an erasure code is also stored in several OSDs. In this way, even if a fault occurs in some of the OSDs, the object can be restored from the remaining OSDs according to a restoration algorithm.
However, if data in some of the OSDs in FIG. 1 needs to be modified, typically, data needs to be rewritten into all OSDs in an object-based storage system, which increases network traffic and a disk input/output (IO) throughput in the object-based storage system, causing a waste of system resources, where the waste of system resources herein is also referred to as a write penalty.